Contact Modelling among Wires in the Mechanical Characterization of Mesh Reflectors

Large Deployable Reflectors have become crucial for earth observation, scientific missions, and space communications. Reflector meshes are made of metal wires, forming a repetitive pattern of numerous loops in reciprocal contact. During the operational transmission/reception of electromagnetic waves, unwanted intermodulation products affect the signal-to-noise ratio due to uncertainties in electrical contacts. The mesh has an almost planar shape, but the physical contacts among the wires would require 3D modelling. The direct approach with 3D FEM models, even if implemented through one-dimensional elements (the wires), often leads to simulations presenting convergence difficulties already with very small mesh portions. Possible alternative strategies consist of a 2D approach to the problem and appropriate tricks to make the convergence easier, such as using contacts activated through fictitious point elements placed between wires in contact, allowing the sliding between them. This paper presents a new 2D technique for modelling wires adopting a simplified although effective contact algorithm. The wires are subdivided into portions using original curvilinear one-dimensional elements (named Wire elements). The structural modelling of the curvilinear wires is developed in the middle mesh plan. The 2D recognition of the contacts is entrusted on the intersections of the wires to monitor the appearance of contacts. This technique reduces the overall number of DOFs and deals with the sliding among wires simply and automatically. Contact constraints enter into the solver through the method of Lagrange multipliers.